JPH0450710A - Optical measuring head device and its adjusting method - Google Patents

Abstract

PURPOSE:To adjust the focus position of a lens with high accuracy by arranging a light source and a lens at a specific interval, and then putting a temperature controller in operation and varying the temperature of the lens. CONSTITUTION:The set temperature of a temperature control circuit 61 is varied to vary the heating value or heat absorption quantity of the temperature controller, thereby varying the temperature of the lens 25. Then the focus posi tion of the lens 25 is shifted continuously to shape the light, which is projected from a light source through lens 25, for example, into an accurate parallel beam or form a spot on an object body in a specific shape. Further, when the light source and lens 25 are assembled, the interval between the both is prescribed to a specific value to adjust the focus position of the lens 25 roughly, and then the temperature of the lens 25 is varied to adjust the focus position of the lens 25 finely.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical measuring instrument that uses laser light or other light sources.

(Prior Art) Conventionally, a target object is irradiated with a laser beam emitted from a semiconductor laser, and the speckle pattern generated by the diffused light from the object surface is observed, and the speckle pattern caused by movement, deformation, etc. of the object is observed. The amount of movement of the object based on the change,
Methods for measuring the amount of deformation, etc. are known (for example, "Optical Measurement Handbook" published by Shokusen Shoten, pp. 234-24).
(page 5).

However, until now, only the principle of the above measurement method and the basic equipment configuration have been clarified, and the specific arrangement of equipment and detailed structure to improve measurement accuracy have not yet been sufficiently researched. It has not yet been put into practical use.

For example, in order to put a speckle length measuring meter that measures the amount of movement of an object with high precision into practical use, components such as a semiconductor laser, collimator lens, and image sensor must be installed with high precision. Since each was positioned independently, it was difficult to perform highly accurate positioning.

Further, depending on the location where the semiconductor laser is installed, the temperature changes drastically and the oscillation wavelength of the laser largely depends on the temperature. Therefore, in order to improve measurement accuracy, it is necessary to strictly control the temperature of the semiconductor laser.

Therefore, in order to put speckle length measuring meters into practical use, the applicant has developed a measuring head structure that allows each component to be positioned easily and with high precision, and that provides high measurement accuracy regardless of the measurement atmosphere (patent application 2-33306).

FIG. 1 shows the structure of the measurement head described above, in which the measurement head (1) has a semiconductor laser unit (2
), electronic cooling device (3), -dimensional image sensor - (4
) etc. are deployed. The semiconductor laser unit (2) is
It is constructed by arranging a semiconductor laser, a collimator lens, etc. inside a temperature control housing (22).

As shown in FIG. 2, the collimator lens (25) is fixed to the end of a beam adjustment screw tube (26), and the screw tube is screwed into the screw hole (24) of the temperature control housing (22) to create a storage chamber. (23).

When assembling the measurement head (1), the beam adjustment screw tube (26) is screwed into the temperature control housing (22) and rotated in forward and reverse directions to align the semiconductor laser (21) and collimator lens (25). The interval is adjusted, thereby shaping the laser beam emitted from the collimator lens (25) into a parallel beam.

According to the above measurement head structure, if the measurement head (1) is installed with high precision, each component within the casing (10) will be positioned with high precision at the same time, making highly accurate length measurement possible. Become.

(Problem to be Solved) However, in the measurement head structure described above, in the assembly process of the measurement head (1), the beam adjustment screw cylinder (26) inside the temperature control housing (22) is rotated in forward and reverse directions. Semiconductor laser (21) and collimator lens (2
5), when adjusting the interval between the temperature control I roll housing (22) screw hole (24) and the beam adjustment screw tube (2
6) was unavoidable and caused adjustment errors.

An object of the present invention is to provide an optical measurement head device that can adjust the focal position of a collimator lens (25) with high precision.

(Means for Solving the Problems) In the optical measuring head device according to the present invention, the measuring head (1) includes a light source, a lens (25) through which the light from the light source is transmitted, and a lens (25) that has a heat generating or absorbing effect. and a temperature sensor (6), the lens (2)
5) is made of optical plastic. A temperature control circuit (61) that emits a control signal according to the difference between an arbitrary set temperature and a temperature detected by the temperature sensor (6) is connected to the temperature adjustment device, and is capable of changing the temperature of the lens (25). The focus of the lens is adjusted by.

Further, in the method for adjusting an optical measurement head device according to the present invention, the measurement head device includes a light source, a lens (25) through which the light from the light source is transmitted, and a temperature adjustment device that exhibits heat generation or heat absorption. and the lens (25)
is formed using optical plastic as a material. After the light source and the lens (25) are installed at a predetermined interval, the temperature control device is operated to change the temperature of the lens (25), thereby finely adjusting the focal position of the lens.

(Function) Generally, the refractive index of a plastic lens has extremely high temperature dependence, and it is known that the refractive index of the lens decreases approximately linearly as the temperature increases.

In the above optical measuring head device, the temperature control circuit (
By changing the set temperature of 61), the amount of heat generated or absorbed by the temperature adjustment device changes, and the temperature of the lens (25) can be changed. And with this, the lens (2
By continuously displacing the focal position of 5), it is possible to shape the light emitted from the light source through the lens (25) into, for example, an accurate parallel beam, or to form a spot on the target object into a predetermined shape. .

Furthermore, in the method for adjusting the optical measuring head device,
By setting the distance between the light source and the lens (25) to a predetermined value when assembling the light source and the lens (25), coarse adjustment is made to the focal position of the lens (25), and then by changing the temperature of the lens (25), the distance between the two is set to a predetermined value. The focus position is finely adjusted.

(Effects of the Invention) According to the optical measurement head device and its adjustment method according to the present invention, the focal position is adjusted by changing the temperature of the lens, so mechanical There is no error problem and highly accurate adjustment is possible.

(Example) Hereinafter, an example in which the optical measuring head device according to the present invention is implemented in a speckle length measuring meter will be described with reference to the drawings. Note that the examples are for explaining the present invention,
This invention should not be construed as limiting or reducing the scope of the claimed invention.

As shown in FIG. 1, the measurement head (1) includes a semiconductor laser unit (2), an electronic cooling device (3), and an image sensor (4) arranged in one dimension in a sealed casing (10). etc., to form a unit.

As shown in the figure, the casing (10) has a rectangular parallelepiped-shaped main body with an opening on one side, and a rubber gasket (11) that closes the opening.
and a cover (12) are fixed with screws to form a closed container. A window (14) for laser beam emission is provided in the front wall of the casing (1o).

As shown in FIG. 2, the semiconductor laser unit (2) has a laser beam generating section consisting of a semiconductor laser (21), an optical plastic collimator lens (25), etc. built into a temperature control housing (22). It is integrated. The semiconductor laser (21) has a temperature sensor (
6) on the first substrate (5), and the substrate is screwed and fixed to the back of the temperature control housing (22), and the semiconductor laser (21) and the temperature sensor (
6) is housed in the storage chamber (23) within the temperature control housing (22). Further, the temperature control housing (22) is formed with a screw hole (24) communicating with the storage chamber (23).

The collimator lens (25) is fixed to the end of a beam adjusting screw tube (26) formed with an external thread, and is attached to the screw tube (26).
6) into the screw hole (24) of the temperature control housing (22), the collimator lens (25) is housed in the storage chamber (23) or the screw hole (24).

As a result, the accommodation chamber (23) of the temperature control housing (22) contains the substrate (5) and the collimator lens (25).
The semiconductor laser (21
) and a temperature sensor (6) will be placed. Therefore, the temperature sensor (6) and the semiconductor laser (21) are always maintained at the same temperature, and the temperature control of the semiconductor laser (21) is performed accurately without error.

As shown in Figure 3, the temperature control housing (22) is used as a rough adjustment to shape the laser beam (8) emitted from the collimator lens (25) into an accurate parallel beam.
Rotate the beam adjusting screw tube (26) screwed into the beam adjustment screw tube (26) in the forward and reverse directions to align the semiconductor laser (21) and the collimator lens (26).
5) The spacing has been adjusted.

Then, further fine adjustment is performed by adjusting the focus by changing the temperature of the collimator lens (25), which will be described later.

Collimator lens (25) of screw tube (26) for beam adjustment
) A slit plate (27) having a laser beam aperture hole (28) is fixed to the end opposite to the slit plate (27). The inner diameter of the laser beam aperture (28) is set so that the average speckle diameter of the speckle pattern is approximately the same as the arrangement pitch (for example, 13 μm) of the COD constituting the one-dimensional image sensor (4).
Alternatively, it is specified to be slightly larger.

As shown in FIG. 1, a flat electronic cooling device (3) is installed on a base (13) fixed to the bottom surface of the casing (10), and the semiconductor laser is placed in close contact with the top surface of the electronic cooling device (3). Unit (2) is fixed.

As shown in Fig. 4, the electronic cooling device (3) has a large number of P-type semiconductors (33) between a pair of ceramic plates (31, 32).
) and N-type semiconductors (34) are arranged alternately, and these are connected in -rows by electrode plates (35).
It has a well-known structure in which lead wires (36) and (37) are connected to the leads (35) and (37), respectively.

As shown in FIG. 1, the base (13) has a second substrate (51) at its end on the window (14) side, which has a through hole (53) through which the laser beam from the semiconductor laser unit (2) passes. A dimensional image sensor (4) is installed on the substrate (51).
) is fixed.

Further, inside the casing (10), a third substrate (52) is fixed above the semiconductor laser unit (2).

The first to third substrates (5), (51), and (52) are provided with a circuit for driving the semiconductor laser (21) and a temperature control circuit (for controlling the temperature inside the temperature control housing (22)). 61), as shown in Fig. 6, there is a first stage amplifier (
9) and a buffer amplifier (90) are formed.

The temperature control circuit (61) can have various known configurations, and FIG. 5 shows one example. The circuit includes a PI control circuit (64) as an input section, and an operable temperature setting section (
The set temperature signal from the semiconductor laser unit (65) and the semiconductor laser unit (2
) is inputted with the detected temperature signal from the temperature sensor (6). In addition, the circuit has two power supplies (62) (63)
and two transistors Q1 and Q connected with different polarities.
2, and two lead wires (36 )
(37) is connected.

In the temperature control circuit (61), when the detected temperature is equal to the set temperature, no output is generated in the PI control circuit (64), but when a difference occurs in the same temperature, the PI control circuit (64)
), one of the transistors is turned on, and a positive or negative DC voltage is applied from the power supply (62) or (63) to the lead wire (
36) Output to the electronic cooling device (3) through (38). For example, when the detected temperature is higher than the set temperature, the direction of electricity supply to the electronic cooling device (3) is set so that the electronic cooling device (3) exhibits an endothermic effect. As a result,
The temperature inside the semiconductor laser unit (2) is controlled by the temperature setting section (
65) will be maintained at the set temperature.

The temperature control circuit (61) plays the role of maintaining the semiconductor laser (21) in the semiconductor laser unit (2) at a constant temperature and its oscillation wavelength at a constant value during length measurement. When assembling the unit (2), it is used to adjust the focus of the collimator lens (25).

Generally, the refractive index of a plastic lens has extremely high temperature dependence, and it is known that the refractive index of the lens decreases approximately linearly as the temperature increases.

For example, PM is used as the optical material of the collimator lens (25).
When MA is used, the refractive index temperature coefficient of PMMA is 10
~1.2 x 10-'/°C, which is much larger than the temperature coefficient of refractive index of optical glasses (2-5 x to-'/°C).

Furthermore, it is known from optical analysis that the following relationship holds between the temperature change amount /T and the change amount 7F in the focal length F of the lens.

JF=(-nF+αF)
00 mm, the following relational expression is obtained.

ΔF=3. lX1O-27T Therefore, a focal displacement of 0.03 mm will occur for a temperature increase of 1°C.

In the assembly process of the measurement head (1) shown in FIGS. 1 and 2, first, as a rough adjustment, the beam adjustment screw cylinder (26) inside the temperature/control housing (22) is rotated in forward and reverse directions. After setting the distance between the semiconductor laser (21) and the collimator lens (25) to a predetermined value, the position of the beam adjusting screw tube (26) is fixed using an adhesive or other fixing device. After the assembly is completed, as a final fine adjustment, operate the temperature setting section (65) shown in Fig. 5 to change the focal point due to the temperature change of the collimator lens (25).
The focal point of the collimator lens is made to coincide with the point light source position of the semiconductor laser (21).

In addition, in the above-mentioned fine adjustment, an actual length measurement is performed using a focus adjustment jig equipped with a micrometer, etc., as the object to be moved, and the temperature is adjusted to obtain accurate length measurement results. This can be done by operating the setting section (65).

FIG. 6 shows an example of the configuration of an external circuit connected to the measurement head (1) to calculate and display the amount of movement of an object based on the image signal from the -dimensional image sensor (4). It shows.

As is well known, the dimensional image sensor (4) repeats scanning in the COD array direction at regular intervals in response to a reset signal, a start signal, and a shift signal sent from the buffer amplifier (90). The output signal of the sensor (4) is sent to the sample hold circuit (91) via the first stage amplifier (9).
This eliminates noise specific to CCDs.

The output signal of the sample and hold circuit (91) is sent to the binarization circuit (93) via the gain control amplifier (92), where the image signal is binarized, and the binarized data is sent to the correlator (94). ), the cross-correlation function between the speckle pattern at the reference position of the target object and the speckle pattern after movement is sequentially calculated while shifting the reference position, and the calculation results are sent to the microcomputer (
96). The microcomputer (96) calculates the moving distance of the object from the peak position of the cross-correlation function, and displays the result digitally on the display (97).

Further, the operations of the buffer amplifier (90), sample hold circuit (91), binarization circuit (93), and correlator (94) are controlled by timing signals supplied from a timing signal generator (95). There is.

During measurement, the measurement head (1) shown in FIG. ) is installed parallel to the direction of movement.

In this state, the circuit shown in FIG. 6 is operated to measure the moving distance of the target object.

According to the speckle length measuring needle, by accurately installing the casing (10) of the measuring head (1), the semiconductor laser (21), collimator lens (25) and -dimensional image sensor inside the casing (10) can be simultaneously installed. −(
4) will be positioned with high precision. or,
By equipping the electronic cooling device (8) and the temperature control circuit (61), the oscillation wavelength of the semiconductor laser (21) can be maintained at a constant value regardless of the installation environment of the measurement head (1), and the laser beam can be controlled accurately. It can be formed into a parallel beam, thereby achieving high length measurement accuracy.

The above description of the embodiments is for illustrating the present invention, and should not be construed to limit or reduce the scope of the invention described in the claims.

Further, the configuration of each part of the present invention is not limited to the above embodiments, and various modifications can be made within the technical scope of the claims.

For example, the temperature control circuit (61) is not limited to the one shown in FIG. 5, and it goes without saying that various well-known circuits, such as one using PID control, can be employed.

Furthermore, the present invention is applicable not only to speckle length measuring instruments using the laser described above, but also to various optical measuring instruments such as photoelectric switches using LEDs, displacement meters using LEDs or lasers, speedometers, and external shape measuring instruments. Furthermore, the light to be irradiated onto the target object is not limited to a parallel beam, but various types of light can be used, such as one that forms a predetermined spot on the target object, or one that repeatedly scans the surface of the target object. .

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway exploded perspective view of a measuring head according to the present invention, FIG. 2 is an exploded perspective view of a semiconductor laser unit, FIG. 3 is a side view illustrating the positional relationship between the semiconductor laser and the collimator lens, and FIG. FIG. 5 is a sectional view of the electronic cooling device, FIG. 5 is a block diagram showing the configuration of the temperature control circuit, and FIG. 6 is a block diagram of the measurement circuit to be connected to the measurement head. (1)...Measuring head (14)...Window (25)...Collimator lens (4)...Image sensor (10)...Casing (21)...Semiconductor laser (3) ...Electronic cooling device (6) ...Temperature sensor

Claims (1)

[Scope of Claims] (1) In an optical measurement head device including a measurement head (1) that emits light from a light source toward an object to be measured via a lens, the measurement head (1) is connected to the light source. , a lens (25) through which the light from the light source should pass, a temperature control device that exhibits heat generation or heat absorption, and a temperature sensor (6).
The lens (25) is made of optical plastic, and the temperature control device has a temperature control signal that generates a control signal according to the difference between an arbitrary set temperature and the temperature detected by the temperature sensor (6). An optical measuring head device, characterized in that a control circuit (61) is connected to the lens (25), and the focus of the lens (25) is adjusted by changing the temperature of the lens. (2) In a device that irradiates the surface of a moving object to be measured with a laser beam and measures the moving distance of the object based on the light reflected from the object, a casing ( 10) includes a semiconductor laser (21), a collimator lens (25) that focuses the laser light from the semiconductor laser (21) to form a laser beam, and a temperature control device that exhibits heat generation or endothermic action. , a temperature sensor (6) are disposed to constitute the measurement head (1), the collimator lens (25) is made of optical plastic, and the temperature adjustment device includes an arbitrary set temperature and the temperature sensor. (6) Temperature control circuit (61) that emits a control signal according to the difference from the detected temperature.
) is connected to the collimator lens (25), and the focus of the collimator lens (25) is adjusted by changing the temperature of the collimator lens (25). (3) Semiconductor laser (21), collimator lens (25)
) and the temperature sensor (6) are arranged in a storage chamber (23) provided in the integrated temperature control housing (22), and are in close contact with the outer surface of the temperature control housing (22) to serve as the temperature adjustment device. The optical measuring head device according to claim 2, further comprising an electronic cooling device (3). (4) In a method for adjusting an optical measurement head device including a measurement head (1) that emits light from a light source toward an object to be measured via a lens, the measurement head (1) includes a light source and a light source. The lens (25) is composed of a lens (25) through which light is transmitted, and a temperature control device that exhibits heat generation or heat absorption.The lens (25) is made of optical plastic, and the light source and the lens (25) are A method for adjusting an optical measurement head device, characterized in that after the lenses (25) are installed at predetermined intervals, the temperature adjustment device is operated to change the temperature of the lens (25), thereby finely adjusting the focal position of the lens (25). (5) In a method for adjusting a measurement head device in which the surface of a moving object to be measured is irradiated with a laser beam and the moving distance of the object is measured based on the light reflected from the object, the laser beam exit window (14 ) having a casing (10)
a semiconductor laser (21);
The measurement head (1) is configured by arranging a collimator lens (25) that condenses laser light from the collimator lens (25) to form a laser beam, and a temperature control device that exhibits heat-generating or endothermic action. 25) is made of optical plastic, and after installing the semiconductor laser (21) and the collimator lens (25) at a predetermined interval, the temperature control device is operated to change the temperature of the collimator lens (25). A method for adjusting an optical measurement head device, comprising finely adjusting the focal position of the collimator lens.